Suspensions are devices interposed between two vibrating or tilting mechanical systems, herein referred to as source body, e.g. wheels, and receiving body, e.g. a vehicle cabin, respectively, in order to reduce the forces acting on the receiving body, and/or the displacement thereof, and/or the speed thereof, or combinations of the previous physical magnitudes and/or of any other ones, which are produced on the receiving itself due to the motion or forces to which the source is subjected.
It is widely known that they are arranged in particular between the wheels of the vehicles and the structures of the vehicles used for loading goods or passengers, aiming at avoiding that impacts or vibrations generated during the movement are transmitted to the entire vehicle.
In order to improve the adaptation ability of the suspensions to the various loading and speed conditions, several systems have been manufactured, comprising elastic elements, e.g. metal components, compressed gases, energy dissipating elements, either by means of friction between fluid and solid, and between solid and solid, or by means of suitable electromagnetic couplings the damping ability of which can be automatically varied by a suitable control system according to the operating conditions of the suspension.
A type of suspension giving good results is the sky-hook and ground-hook type devices described in D. Karnopp, M. J. Crosby and R. A. Harwood. (1974). Vibration Control Using Semi-Active Force Generators. Journal of Engineering for Industry, 96(2): 619-626 and in Valasek, M. and Kortüm W. (2002). Semi-Active Suspension Systems II. The Mechanical Systems Design Handbook. CRC Press LLC. They achieved considerable technical and commercial success in the field of semi-active damping control in vibrating systems. The most apparent advantage of these systems is that they are devices having a semi-active operation, i.e. characterized only by the possibility to change their dissipation abilities without a significant external energy supply, hence ensuring constructional simplicity, low costs, reduced weight and size.
A solution providing for a suspension where the features of damping, stiffness and stroke between a vehicle wheel and chassis can be adjusted independently of one another is disclosed in the publication US2005242532A1. However, the ability of this solution to react to impacts and vibrations is limited and does not respond properly to vibrations with a higher frequency.
However, such suspensions leave room for further improvement in the damping performance and flexibility of using the suspensions in wider fields than the vibrating structures. Therefore, a need is felt to manufacture a novel suspension which has superior performance compared to that of the prior art and improves the damping effects on the receiving structure.